The two major harbors for recreational fishing are Lahaina Harbor and Maalaea Harbor. Other harbors include Kahului (the island's "industrial" harbor), and Hana. There are also two small boat ramps where a few of the trailer boats depart from - Mala Wharf in Kaanapali, and Keawakapu, better known as the "Kihei Boat Ramp". Most of the boats I recommend leave from either Maalaea or Lahaina.
If you're staying in Kaanapali, Kapalua, Kahana, or Napili, Lahaina Harbor is the closest. Maalaea is recommended for people staying in Kihei, Wailea or Makena.
Hawaii is one of the only places in the world where you can fish year 'round and still have an excellent chance of landing a really big fish. Marlin, Ono, Ahi and bottom fish can be taken in all months of the year. For a month by month breakdown, click here.
"What's the weather going to be like?" Man, I hear that question a lot! If I knew that I'd make a lot more money than I ever did fishing! Current weather conditions can be found here.
A while back someone threatened to sue me for not informing him it would be a "New Moon" and fishing would be poor. Frankly, I don't put much stock in these kind of fishing forecasts, but just to cover my butt, here's a fun little tool courtesy of the U.S. Naval Observatory.
Select the month and day you're thinking of going out fishing and click "Show Phase". You'll be shown the phase of the moon on that date at 8:00am Pacific Time.
Interested in what the tides are doing the day you plan to go fishing? Choose a day and press "Show Tides". This will give you graphic results of the estimated tidal movement off south Maui for this day. Once the results appear, you can fool around with dates, locations, chart presentations and more nifty options.